This invention relates to the catalytic conversion of coal to produce valuable coal-derived liquids and in particular, to a method for enhancing the conversion of coal to ethyl acetate-soluble components.
A wide variety of processes have been proposed in the prior art for conversion of coal to liquid products. It is recognized that asphaltenes can be detrimental to heterogeneous catalysts employed in catalytic coal liquefaction processes. See, for example, U.S. Pat. No. 4,152,244 to Raichle et al. which discloses a process wherein asphaltenes are removed from a dissolved coal product prior to catalytic hydrocracking. Another approach is described in U.S. Pat. No. 4,081,360 to Tan et al. wherein solvent properties are controlled to suppress the formation of asphaltenes during coal liquefaction.
It is recognized that mineral matter in coal can function catalytically in the coal liquefaction process and a process employing minerals recycle is disclosed in U.S. Pat. No. 4,211,631 to Carr et al. A number of workers have employed antisolvents to facilitate solids separation in coal liquefaction processes; see, for example, U.S. Pat. No. 3,852,183 to Snell and U.S. Pat. No. 4,075,080 to Gorin. Other coal liquefaction processes which employ organic materials to aid in solids separation include those disclosed in U.S. Pat. Nos. 4,029,567, 4,102,744, and 4,244,812. Neither of the above processes, however, recognize the advantages of recycling a specific portion of ethyl acetate-insoluble materials.